An overview of some aspects of psychiatric epidemiology with special relevance to trainee psychiatrists in the UK

1. Epidemiology 2 Digby Tantam Clinical Professor of Psychotherapy, ScHARR Honorary Consultant Psychotherapist and Psychiatrist Honorary Senior Visiting Research Fellow, University of Cambridge

11. Stem and leaf plots are a way of presenting numerical data. The data found on the left hand side of the solid line is considered the stem, and the numbers on the right are the leaves. This particular stem and leaf plot depicts infant mortality rates in Western Africa. The rates range from 51 to 151. This stem and leaf plot was taken from http://mainland.cctt.org/mathsummer/JosephBond/StemAndPlots/images/table2.gif

17. Inception rate Incidence rate Prevalence Odds

19. Scale Level Scale of Measurement Scale Qualities Example(s) 4 Ratio (scale for SPSS) Magnitude Equal Intervals Absolute Zero Age, Height, Weight, Percentage Geometric mean, log transform 3 Interval (scale for SPSS) Magnitude Equal Intervals Temperature 2 Ordinal Magnitude Likert Scale, Anything rank ordered 1 Nominal (categorical) None Names, Lists of words 0 Dichotomous: both nominal, and pseudo-interval None, but can be combined Yes/ No

20. Visual analogue scale Is this a Likert scale?

40. Copyright ©1994 BMJ Publishing Group Ltd. Altman, D G et al. BMJ 1994;309:188 FIG 1 (left) – Receiver operating characteristic curve Distribution of values of an index of mixed epidermal cell lymphocyte reactions in patients who did or did not develop grafts versus host disease3 Area under the curve is the ‘diagnostic accuracy’

41. Which has the greater diagnostic accuracy?

46. Classification of the trinucleotide repeat, and resulting disease status, depends on the number of CAG repeats [13] Repeat count Classification Disease status <28 Normal Unaffected 28–35 Intermediate Unaffected 36–40 Reduced Penetrance +/- Affected >40 Full Penetrance Affected

53. Association between hay fever and eczema in 11 year old children 1 From BMJ 2000;320:1468 ( 27 May ) Eczema Hay fever Total Yes No Yes 141 420 561 No 928 13 525 14 453 Total 1069 13 945 15 522